Production of gasoline



p 10, 1946- L. G. HALL ETAL PRODUCTION OF GASOLINE Filed June 11, 1945 LutuvL 33:3

N mm 0 3 L 2 4% 9 n mm 8 a 2 m m 6 a a. n 2 mm w. 0 R Q ..LHv H figs, R 8 0N w m co ficuvevaz ,1 m M 9 Q Q fi. 4V

Patented Sept. 10, 1946 PRODUCTION OF GASOLINE Larry G. .Hall, St. Louis, Mo., and Herman G.

Boucher, Wood River, 111., assignors to Shell Development Company, San Francisco, Calif., a

corporation of Delaware Application June 11, 1945, SerialNo..598,708

7 Claims.

gasoline .from a. given quantity of crude petroleum in the most economical manner. Thus, the criterion of .the production obtained is not merely the number of barrels of gasoline produced per barrel of crude, nor the quality of the gasoline, but a combination of these hereinafter referred to as quality-barrel. The term "quality in this expression is a weighted numerical index of quality such as octane number or such other index as may-be suitable. In general the quality of gasoline is fixed by specification and the refiner then strives to produce the maximum amount of material .meeting such specifications.

In the usual practice the first step in the production of gasoline from petroleum is to separate gasoline constituents naturally occurring therein. This is efiected by a simple topping operation. The product is known as straight run gasoline. Straight rungasoline .consists essentially of saturated hydrocarbons and contains only small amounts of impurities which, due to their character, are, jfurthermor'e, relatively easily removed. It therefore generally requires and is given only a light acid refining treatment. .Straightrun gasoline, however, generally has very poor antiknock characteristics :and is consequently of poor quality.

The material remaining after Ltopping to remove straight run gasoline is usually separated somewhatfurther into one or more-suchproducts as-kerosene, naphtha, stove .oil, gas oil, and reduced crude. One or more of .these products is then cracked by various conventional cracking processes to produce additional amounts of gasoline. Any of the conventional cracking processes producing an olefinic high anti-knock gasoline product may be employed. However, in conventional practice, catalytic cracking with clay-type cracking catalysts is preferred since .such. processesproduce gasoline of superior quality.

The cracked gasolines contain appreciable amounts of sulfur compounds, nitrogen compounds, diolefins, acetylenic compounds, and other materials which are diflioult to remove by ord-lnaryirefining methods without large losses of material and considerable depreciation of the anti-knock properties of the gasoline. Refining by conventional acid treating followed by doctor treating and rerunning has the recognized disadvantages of high acid consumption, poor-yields and depreciation of the anti-knock properties. In View .of these disadvantages such materials are sometimes refined by catalytic methods referred to generally as hydrofining. In this refining method'the material is treated under .hydrogen pressure in the presenceof asuitable hydrogenation catalyst. The chief advantage of hydrofining over conventional acid refining methods is that the material may be refined with. less loss of material. However, hydrofining, as practiced at present, is not Wholly satisfactory. The process consumes considerable amounts of expensive hydrogen; furthermore, a considerable loss in antiknock characteristics is usually caused by the saturation of at least part. of the olefinic and/or aromatic constituents of the gasoline.

The refined cracked gasoline is then blended with the maximum amount of the refined straight run gasoline that can be tolerated while still maintaining the desired quality of the blend.

It will be appreciated that the refinergusually has at his disposal one or more additives such as alkylate, isopentane, aromatic extract, cumene, xylidine, tetraethyl lead, etc., which are usually added to the blend of cracked and straight run gasoline to produce the final gasoline product. However, the amount of such additives that can be addedxto the blend .of cracked and straight run gasoline (sometimes referred to as base stock) is limited by the limited availability of the'additives or by specifications of such factors as heat content, volatility, corrosiveness, and the like. The minimum quality oi the blend of cracked and straight run gasoline produced by the refiner is therefore usually below that of the finished gasoline and is determined by the amount of such additivesavailable .for use.

In the process of the present invention straight run gasoline and cracked gasoline are produced from petroleum in the above described general manner. The invention lies in the particular methodof handling these materials to produce the finished blend. The cracked gasoline may be produced from any portion of the petroleum boiling above the gasoline desired and may be produced by any of the conventional cracking and/orreforming methods which produce ahigh anti-knock olefinic gasoline. A preferred method is, by the catalytic cracking of petroleum oils with clay-type catalyst, Such processes are, for

removing iron-bearing impurities, leaching outalumina, adjusting the ratio of silica to alumina, and/or by incorporating minor amounts of promoters in order to increas their activity, stability, etc., or to reduce their carbon-forming tend ency. Various synthetic clay-type cracking catalysts are also now widely used. These catalysts consist largely of silica and/oraluminaand/or magnesia and are often modified by minor amounts of such materials as BzOs, AlFs, A1PO4, ZIOz, etc. Also certain promoters may be introduced along with the hydrocarbon stream entering the reaction zone. Such promoters include boric oxide, hydro-gen, halides, organic halides, etc. The specific catalyst forms no part of the present invention and will not be described in further detail.

' In these processes the oil to be cracked is contacted, usually in the vapor phase, with the catalyst under suitable conditions of pressure and residence time at a temperature usually in the order of 750 F. to 1200 F. depending upon the particular hydrocarbon feed, the particular catalyst, and the particular results desired.

' According to the process of the present invention there is separated from the cracked gasoline prior to further handling an olefinic fraction consisting largely of Ceor C6-C7 hydrocarbons. Likewise there is separated from th straight run gasoline prior to refining a substantially saturated fraction consisting largely of Ce hydrocarbons. The separated straight run fraction is blended with the remaining cracked gasoline. Thus, the separated straight run fraction is subs'tituted for the separated cracked fraction in the cracked gasoline. The two materials resulting'are separately refined and then reblended. In a preferred embodiment of the invention the separated cracked fraction is also blended with a remaining portion of the straight run gasoline; thus the separated cracked fraction is also substituted for the separated straight run fraction in the straight run gasoline.

' The catalytic gasoline containing the separated straight run fraction is mixed with a hydrogencontaining gas and contacted with a hydrogenation catalyst, i. e., hydrofined, The hydrofining treatment may be carried out with any of the catalysts commonly employed and recommended for this process. Examples of suitable catalysts are the oxides and sulfides of V, Cr, Mn, Fe, Co, v

Ni, M and W. Particularly suitable catalysts comprise a sulfide of a metal of the iron group, preferably in combination with a sulfide of a metal of group VI of the periodic system of the elements. Examples of such preferred catalysts are nickel sulfide, iron sulfide, cobalt sulfide, alone and in combination with sulfides of molybdenum or tungsten. These catalysts may generally be used substantially continuously for hundreds of hours without regeneration. The treatment is carried out in the presence of an excess of hydrogen. The amount of hydrogen employed is in general between about 1 and 30 mols per mol of hydrocarbon feed. (Only a portion of this hydrogen is consumed.) sure may vary over a wide range. Pressures in The presth order of 200-2000pounds per square inch are illustrative. The hydrofining treatment may be advantageously carried out at temperatures ranging from about 400 F. to about 1000 F. When the material treated is high in sulfur (for example containing more than about 0.1%. sulfur) low temperatures (below about F.) consistent with the activity of the catalyst and the other treating conditions are generally preferred. If

the material treated is low in sulfur (for example containing less than about 0.1% sulfur) higher temperatures (for example, between about 850F. and 1000F;) may be preferred. The treatment afforded may be the minimum treatment consistent with the desired degree of refining (as measured by the sulfur content, gum-forming tendency, etc); this allows the treatment to be effected with a minimum hydrogen consumption and results in the minimum loss of anti-knock properties. .In some cases, however, a more thorough treatment toproduce a substantially saturated product (particularly when operating at the higher temperature levels) may be more advantageous;

The separated cracked gasoline fraction consisting largely of Ce hydrocarbons is subjected to a separate non-hydrogenating refining treat ment. A preferred treatment is a conventional acid refining treatment, for example, with sulfuric acid or spent alkylation acid (HzSOi). The treatment is carried out under conditions of acid concentration, temperature, time, etc., and in the known manner to the extent necessary to provide a suitable refining. The exact strength and/or amount of acid required will depend to a certain extent upon the amount of unsaturated hydrocarbons present in the material treated and to a certain extent upon the conditions employed in the treating step. Any suitable method of contacting the gasoline with the acid may be used and since such methods are well known there is no need to describe them in detail.

The separated cracked gasoline fraction may, in general, be more advantageously treated in a blend with a remaining portion of the straight run gasoline. Thus, according to a preferred embodiment of the invention the separated cracked fraction is blended with a. portion of the remaining straight run gasoline (such portion being the remaining tolerable straight run material above the separated straight run fraction .blendedwith' the remaining cracked gasoline) stock) having the necessary quality. To the base stock blend there is usually then added various amounts of one or more additives in accordance "withtheir availability and with due regard to specifications to produce the final gasoline of the specified'quality. j

Although the novel features which are believed to be characteristic of the process of the invention are mentioned above and are particularly pointed out i the claims appended hereto, the process. ma perhaps be better understood by referring to the following'mor'e detailed descripcracking reactor.

monies tion in wliich specifio preferred embodiments are setforth. To assist in this description-reference is had to the -attached? drawing-wherein there is shown by conventional fl'gures" a: simplified flow diagram of a typical application of the process oftheinvention:

Referring to the drawing; the feedentering via line 2 -istopped topping; column I to= recover overheada light straight run-fraction containing substantiallyall; of the C6 hydrocarbons and if desireda portion of the CFHXdi'OCaI'B'OIIS; This overheadf fraction-is passed via= line 3-tb fractionating column 4' whereinit is separated int'oa l'ower'b'oi-ling overhead fraction containing sub stant'ially'all' of-theconstituentsup through pentaneW-hichi's'withdraWn via line 5, andi a higher boiling "fraction consisting largely' of the strai'ght run (it hydrocarbons which is withdrawn via line 6% Thelower boiling*material'fwitlidrawnvia line 5} may betreated and /or utilized in any die-- sired manner. The straight I run fraction withdrawn via line 6- is=combined with the deliexanized cracked gasoline as hereinafter described:

The topped feed removed from column I via line T ispassed toa," fractionatin'g column 8 wherein a further portion of straight runligasoline-is separated? The amount of straightrun gasoline separated and removed overhead v-iarline 9 is preferably adjusted with respecttuthemaximum tolerable amountotstraight run gasoline tobe included in the finished gasoline. Thus, for example, in a typical operation the material removedifrom fractionating-column 8 via 1ine 9 mayheme anend point -of, for. instance 185i E. This material is combined; with the.- cracked. Cs fraction as hereinafterdescrib'edi The bottom product" irom fractionazton 81? is passed via 1ine- Hi-toa further fractionating col;- umn H to remove additionalg'materialisuch: as naphthankerosene, or the. like. Such materials areremoved overheadvialine l2 and may be treatedand/o'r used in anydesiredflmanner. The higher,boilingresiduefrom fractionator. H" (reduced crude)? is passedvialinessw' and If to a suitable heater l5'and tar separator l6. Heavy residue or taro is removedpvia line I'L vaporized material'i'stllenpassed'via, line l8 to a cracking reactor, [9? wherein it is cracked in theconventionalmanner. with one ofithe conventional claytypei cracking, catalysts, The; cracked product leaves 'the cracking reactor via line and passes to a, fi'actionating column' 2'! wherein the convertedllproducts are separated from unconverted and'insufflcientl'y. converted material; This'lat t'er. material may be withdrawn Via line" 22"v or recyclediin Whole or in. part Vi'a. line; 13 to" the The converted products consistingessentially of gasoline and gases passes over-lieadfrom fractionator" 21' viailine' 24 to a cooler 25 andseparator. 2B;

The 'vaporous product from separator 26 is withdrawn via linet2'l, compressed by compressor 28, and passed to a typical adsorption system. Thus, this vaporous product" is contacted under 'pressure in absorber'29 with a suitable naphtha or=oil fraction recirculated via" line 38. Dry: gas is' removedfrom'the absorbers-via line*3l. The absorber liquid containing: the absorbed; hydro;- carbon-s passes via line 32 to a: stripping column 33 Theconditions:instrippin'gg-column 33; are adjusted to=remove as'an overhead product substantially all "of the absorbed material up through normal pentane; which product is removed via line 341. The. absorberoil thenpasses via'line 35 to a further stripping'column-36. Tlieconditions '6 strippingcolumn 3 6 are adjusted toremoveas an overheadiproducta: cracked gasoline fraction consisting largely of Ge: hydrocarbons: which is removed via line 31. The: stripped absorber oil i's recycled to theiabsorbe'r via line 30.1

The liquid hydrocarbon from separators- 252' is passed Via; line 38 150 a fractionatin'g columns 392.. The conditions in fractionatin'g.v column 39 are 7 hydrocarhonsawhich is removedtvialinefl; This (3s .frac-tioniis :combin'ed with the 1 crackediCs; fracationi removed from: the stripper? 35 via; line; 3:1; The: combined fractions; are; blendect with: the straight: runmaterial; and separately treated; as hereinafter described-s Thdcrackedigasoline fromwl'ii'chtheflCs hydro:- carboni fraction: has: been removed, is; withdrawn from fractionating columnist): via line 44; This material; may: be; out? to; a: desired end-point in fractionatingmolumn 451. The overhead product from: fractionator? 4'51- withdrawn ,viailinei 46; iSEthB crac-lsed: gasoline; fractiom from. which the: Cathy drocarbonshavesbeenzsubstantially remoyedsn The Ca; hydrocarbom fraction removed; from the crackedrgasoline as hereinbeforeadescribediisisub stitutefd? on'replace'd; by: the: straight: run fraction separated: as; hereinbefore: described... Bhusg, the

straightrun: fractionawithdrawrr from: fractionat in column 4: viazlinet 6., is; blended; with; the CV81? head; product: from: fractionating; column 45. This blend: is; mixedi with: an excess of: hydrogen (with respect to that required;f0r;:-complete;sate uration: of: thergasolinel' entering'vialine 41.; For example; the amountazof' hydrogen: introduced Via linet?" may bGLG? molsvper mol of hydrocarbon feed. Tliexmixture preheated. to: a suitable; reaction; temperatures (for example-850? F2) in a suitablepreheaten' 48'.- and:' passedtto catalytic: reactor: 49.. Reactor 49 contains acsuitablerhydro g'enatiorr-dehydrogenationz catalyst-- such, for. example; as; at pelleted :7 mixture of nickel: sulfidetungsterr sulfide; The conditions of pressure. and contactrtimeamay be. adjusted: to. effect. a: substantiallv: complete hydrogenation of the. olefins. Under such: conditions; the": sulfur; compounds and/or:- nitrogerr compounds: will' be; 1argely,re.- moved or: decomposed: and; a1so= dehydrogenation ofinaphthenicz constituents of: .the feed may take place. Typical conditions; are, for example; a pressure-50f aboutz850 p.- s. i andeatliquid hourly space velocity of. about 4. The productwithdrawn viaelineillr is passed to aconventional separating ,andlrecoveryisystemillustrateddiagrammatically in..the drawing by a single separator 5|. Gas rich inhydrogeniswithdrawn from the; separator 5| and recycled via pump 52" and line 41. In order to maintain a suitable concentration ofhydrogen inther recycle" gas some of this gas'may'be withdrawn? from the system via line 53' and make-up hydrogen may beadded via-linei l. The hydrofined blendof cracked and straight run gasoline withdrawn from separator 5| vialine '5 S'isblended with theacid treated blend or straight run gasoline and" cracked gasoline as hereinafter described and treated by suitable means to: remove hydrogen' sulfide formed in' thehydrofining treatment. Thus, the hydrofined gasoline is :mixed with causatic' solution= enteringviaeline- 56: and. passed tm a caustic treater 51. The product is withdrawn to a settler 58. Caustic solution is recycled via line 56. Make-up caustic is added via line 59.

The straight ,run gasoline from which the C6 hydrocarbons, and if desired also some of the C7 hydrocarbons, have been removed as hereinbefore described (withdrawn from fractionating column 8 via line 9) is blended withthe combined catalytic Cs fractions separated a hereinbefore defined (entering via lines 3'! and 42). This blend passes via line 31 to an acid treater 60 wherein it is contacted with sulfuric acid, spent alkylation acid, or other suitable acid under conditions chosen with respect to the particular feed to afford the degree of refining required for the particular gasoline being produced. In the production of automotive gasoline, for example, a very mild refining treatment at low temperature and with relatively dilute acid may be sufiicient. In the production of certain types of aviation gasoline, on the other hand, a relatively severe treatment with a more concentrated acid may be required. The acid treated material is withdrawn to a separator Bl. Acid is recycled via line 62. Make-up acid is added via line 63. The acid treated material is withdrawn from the separator via line 64. This material is combined with the hydrofined blend of cracked and straight run material from line 55 and is neutralized in the caustic scrubber 51. The finished blend or base stock consisting of straight run gasoline and cracked gasoline properly refined and in the desired proportions is withdrawn via line 65. In general a portion of the cracked C fraction is included in the finished gasoline. This material requires a caustic treatment to remove mercaptans and hydrogen sulfide. This material, withdrawn via line 34, may be blended with the gasoline entering the caustic treater.

It will be appreciated that the system described above and illustrated in the drawing is merely a typical example of the process of the invention and may be modified in various particulars. For example, the hydrofined blend and the acid treated blend y be caustic treated separately and each or both of them may be cut to the desired gasoline end-point (rerun) prior to the final blending. Also, for example, in actual practice the separation and recovery system illustrated by the simple separator 5! may be complicated by a system for removing hydrogen sulfide from the recycled hydrogen stream and/ or by the utilization of multiple compression and cooling steps. Also, the combinations of fractionating equipment and method of handling to recover and separate the specified fractions may be altered Without departing from the spirit of the invention. It is not essential that the cracked gasoline and straight run gasoline be derived from the same petroleum. The straight run fraction, for example, may be derived from any, preferably naphthenic, petroleum while the cracked gasoline may be derived from the cracking or reforming of any'feed stock. Also, the separation of the respective Cs fractions may be altered or adjusted to afford the optimum production of gasoline according to the circumstances. For example, the straight run fraction containing C's hydrocarbons may be cut to include a considerable portion of C7 hydrocarbons and may be cut in such a manner as to be relatively concentrated in Cs and C7 naphthenes. When the straight run gasoline contains appreciable amounts of naphthenic hydro .carbons (and most straight run gasolines do) this is a very desirable and most advantageous method of operation. V I

The principal advantage of the process of the invention is that it allows the production of gasoline of any specified quality (in which a blend of straight run gasoline and cracked gasoline can be used-and this is in nearly every case) to be appreciably increased without increasing the hydrogen requirement. Thus, for example, in a typical plant producing, for instance, about 9,000 B./D. of aviation base stock with a consumption of 1.57 million cubic feet hydrogen the production may be increased between about and 400 B./D. In many instances the increased production may also be obtained with decreased operating expenses. If for some reason increased volume production is not desired the advantage of the process of the invention may be realized either in the production of an equal volume of gasoline of improved quality or in the production of an equal volume of gasoline of equal quality with decreased consumption of more costly additives.

The advantage of the described method of operation in a typical case is illustrated in the following example in which it is assumed that a refiner with the following materials available de sires to produce the maximum amount of ANF-28 aviation gasoline:

Catalytic cracked depentanized base sto Catalytic cracked C5 fraction 900 Isopentane (95%) 1,840 Debutanized C -C5 alkylate 6, 450

umene l, 000 Hydrogen (million cubic feet) l. 57

In normal operation (case 1) 4000 B./D.'of depentanized catalytic cracked base stock is hydrofined, 1000 'B./D. of depentanized catalytically cracked base stock is acid treated, 1621 B./D. of depentanized straight run base stock is acid treated. The products are then blended. The maximum production of ANF-28 aviation gasoline is 15,265 B./D. When operating according to the process of the invention (case 2) the catalytically cracked Cs fraction andthe straight run Cs fraction are exchanged as described. A blend of 4,500 B./D. of dehexanized catalytically cracked base stock and 1,000 B./D. of the straight run hexane fraction is hydrofined. A blend of 254 B./D. of catalytically cracked C's fraction and 1,150 B./D. of hexanized straight run base stock is acid treated. The materials are then blended. The maximum production of ANF-28 aviation gasoline is 15,625 l3./D. Thus, case 2 affords an increased production of 360 B./D.

Example II Petroleum was topped torecover a straight run gasoline fraction and various intermediates. Catalytically cracked gasoline was produced from various heavy petroleum products by the fluid catalyst cracking process using the present commercial silica-alumina composite cracking catalyst. The straight run gasoline was fractionated to recover separately a fraction consisting essentially of Ce hydrocarbons and then rerun to an end-point of about F. The catalytically cracked product was treated to recover catalytically cracked C5 hydrocarbons and catalytically cracked Cc hydrocarbons separately and topped to produce a dehexanized catalytically cracked gasoline having an end-point of about 325 F. The dehexanized catalytically cracked gasoline was blended with the straight run C6 fraction to produce a feed blend having the following properties:

This blend was hydrofined with a nickel sulfidetungsten sulfide catalyst under the following approximate conditions:

Temperature F 900 Pressure -p. s. i 840 Liquid hourly space velocity 4 -Mol ratio of hydrogen to hydrocarbon 6:1

The product had the properties specified in the above table. The catalytically cracked fraction consisting essentially of Ce hydrocarbons was blended with the straight run gasoline remaining after the separationof the C6 fraction. This blend was treated with about 20 pounds per barrel of spent alkylation acid, caustic washed and rerun. The losses were about 18%. The acid treated blend was then blended with the hydrofined blend to produce the final blend or base stock We claim as our invention:

1. In the production from petroleum of gasoline comprising straight run gasoline and cracked gasoline, the improvement which comprises separating from a cracked gasoline an olefinic fraction consisting largely of Ce hydrocarbons, replacing said separated olefinic fraction with a saturated straight run gasoline fraction consisting largely of C6 and C7 hydrocarbons, subjecting the thus produced blend of said dehexanized cracked gasoline and straight run gasoline fraction to a hydrofining treatment under hydrogen pressure in the presence of a hydrogenation catalyst, subjecting said separated olefinic fraction to an acid refining treatment, and recombining the acid refined material with the hydrofined blend.

2. In the production from petroleum of gaso- I lin comprising straight run gasoline and cracked gasoline, the improvement which comprises separating from a cracked gasoline an olefinic fraction consisting largely of C6 hydrocarbons, replacing said separated olefinic fraction with a saturated straight run gasoline fraction concentrated in C6 and C7 naphthenes, subjecting the thus produced blend of said dehexanized cracked gasoline and straight run gasoline fraction to a hydrofining treatment under hydrogen pressure in the presence of a hydrogenation catalyst, subjecting said separated olefinic fraction to an acid refining treatment, and recombining the acid refined material with the hydrofined blend.

3. In the production from petroleum of gasoline comprising straight run gasoline and cracked gasoline, the improvement which comprises separating from a cracked gasoline an olefinic fraction consisting largely of Ce hydrocarbons, separating from straight run gasoline a saturated fraction consisting largely of Ce hydrocarbons, blending said latter fraction with the remainder of the cracked gasoline, subjecting the blend to a hydrofining treatment under hydrogen pressure in the presence of a hydrogenation catalyst, blending said olefinic fraction separated from the cracked gasoline with the remainder of the straight run gasoline, subjecting this latter blend to an acid refining treatment, and blending the two thus-treated gasolines.

4. In the production from petroleum of gasoline comprising straight run gasoline and cracked gasoline, the improvement which comprises separating from a cracked gasoline an olefinic fraction consisting largely of C6 hydrocarbons, separating from straight run gasoline a saturated fraction relatively concentrated in C6 and C7 naphthenes, blending said latter fraction with the remainder of the cracked gasoline, subjecting the blend to a hydrofining treatment under hydrogen pressure in the. presence of a hydrogenation catalyst, blending said olefinic fraction separated from the cracked gasoline with the remainder of .the straight'run gasoline, subjecting this latter blend to an acid refining treatment, and blending the two thus-treated gasolines.

5. Process according to claim 1 in which the cracked gasoline is a catalytically cracked gasolineobtained by cracking a hydrocarbon oil with a clay type cracking catalyst.

6. Process according to claim 1 in which the hydrofining treatment is carried out with a hydrogenating metal sulfide catalyst. at a temperature of about 850 F. and 1000 F.

7. Process according to claim 1 in which the acid refining treatment is carried out under mild conditions to leave the major portion of the olefine intact.

' LARRY G. HALL. V HERMAN G. BOUCHER. 

